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Source Packet Routing in Networking (SPRING) or Segment Routing

  • Support for RFC 8814  (ACX Series and PTX Series)—Starting in Junos OS Evolved Release 23.4R1, we partially support RFC 8814, Signaling Maximum SID Depth (MSD) Using the Border Gateway Protocol-Link State. Currently, we support signaling the MSD using IS-IS for SRv6. For non-segment routing networks, the MSD value reflects the maximum label depth.

    A controller in a segment routing network learns the MSD of the participating router and computes the segment routing path. The controller ensures that the label stack is not greater than what the routers can support.

    [See Link-State Distribution Using BGP.]

  • BGP classful transport support for IPv4 DTM segment routing traffic engineered (SR-TE) tunnels (PTX10003, PTX10004, PTX10008, and PTX10016)—Starting in Junos OS Evolved Release 23.4R1, we support transport-rib model for V4 DTM SR-TE tunnels by configuring the use-transport-class statement at the [edit dynamic-tunnels tunnel-name spring-te] hierarchy level.

    If the use-transport-class statement is not configured then catch all route and application route is created in the inetcolor.0 table. If the use-transport-class statement is configured then catch all route and application route is created in color.inet.3 table. This behavior is irrespective of including the use-transport-class statement at the [edit protocols source-packet-routing] hierarchy. For dynamic tunnels, SR-TE honors the use-transport-class statement under the dynamic-tunnel configuration rather than source-packet-routing configuration.

    The following IPv4 endpoint for DTM SR-TE tunnels with transport-rib model is supported:

    • DCSPF support (using compute-profile)

    • Dynamic segment list support. Configured segment list must not have any IPv6 address and MPLS SID based of IPv6.

    • Delegation to PCEP controller

    • sBFD support

    • SPRING-TE route is added only into color.inet.3 table

    For IPv4 endpoint for DTM SR-TE tunnels with inetcolor.0 model, if the use-transport-class statement is configured under SR-TE, then dynamically triggered SR-TE tunnel routes is created in both inetcolor.0 table and color.inet.3 table. The use-transport-class statement under dynamic-tunnels hierarchy decides if the SR-TE tunnels need to be placed in color.inet.3 table. SPRING-TE route is added only into inetcolor.0 table for DTM SRTE tunnels for IPv4 endpoints and inetcolor.0 model.

    Traffic steering based on extended color community is supported. For transport-rib model for DTM SR-TE tunnels (IPv4 destinations only), enable the computation and setup of interdomain segment routing paths using express-segments with SR-Policy underlay.

  • Mitigate traffic congestions using tactical traffic engineered (TTE) tunnels (PTX10008 and PTX10016)—Starting with Junos OS Evolved Release 23.4R1, you can avoid congestions on oversubscribed links or domains using the dynamic tactical traffic engineered (TTE) tunnel solution. The dynamic TTE tunnel solution allows you to define congestion for a link by configuring high and low bandwidth thresholds. If the traffic load on the link exceeds the high threshold, then load-sharing is increased. If the traffic load falls below the low threshold, then load-sharing is decreased.

    The TTE solution helps you to:

    • Load-balance traffic towards destination prefixes using the congested outgoing interface or through a dynamically installed Tactical TE (TTE) tunnel..

    • Monitor the cumulative load and subsequent deactivation of the TTE tunnel(s) when congestion is no longer detected.

    To enable congestion protection, include the congestion-protection statement at the [edit routing-options] hierarchy level. Define high and low bandwidth thresholds by including the high-threshold and low-threshold statements at the [edit routing-options congestion-protection template template-name] hierarchy level. You also need to include the export isis-export statement at the [edit protocols isis] hierarchy level.

    The TTE tunnel solution supports ISIS and uses TI-LFA backup routes for congestion mitigation.